Municipal waste water treatment creates sewage sludge in large amounts. Generally, the municipal waste water treatment plant concentrates and dehydrates the sewage sludge to get a dehydrated sludge having a water content of 80% which is transported to other places for further treatments. To facilitate the reduction and reclamation of the dehydrated sludge, it is generally subjected to drying treatment at first.
The commonly used methods for drying sludge include drying in a fluid bed dryer, drying in a multilayer disc drier, film drying, drying in a paddle dryer, and belt drying. The dehydrated sludge is dried directly or indirectly. In the actual drying process, the following problems may occur: (1) the inner parts of the drying device are badly worn, leading to high frequency of the device failure; (2) meddle or high temperature is used for drying, leading to high energy consumption; (3) the treatment of tail gases following the drying is complicated, leading to a high cost; and (4) there is a fair possibility of dust explosions and fires, leading to high dangers.